1. Field of the Invention
This invention relates to apparatus for concurrently moving and guiding sheets of paper into a desired, pre-determined position in a duplicator or printing press. More particularly, but not by way of limitation, the invention relates to apparatus for improving the guiding and registering functions of the conveyance mechanism used on conveyor boards employed in offset duplicators.
2. Brief Description of the Prior Art
Duplicating machines and printing presses frequently include, in association with belt conveyors for moving sheets of paper into and through the machine, some type of structure for retaining the individual sheets in a desired path of movement as the sheets approach and contact the register stops. This structure is intended to prevent rebounding of the paper sheet from the stop after contact therewith, and to prevent buckling or bulging of the paper in a way which interferes with subsequent printing. The structures which have previously been utilized for this purpose have included spheres or balls carried in slots or recesses in bars positioned in the press or duplicator to allow contact and rolling movement of the ball upon the paper as it is driven into the head stop by the belt conveyors. Rollers mounted for rotation about horizontal axes in positions for tangentially contacting the surface of the paper sheets have also been used.
A recent ball-type guidance and registration system utilized for guiding and weighting paper being fed to the head stop or register stop is that shown in U.S. Pat. No. 3,741,536 to Anderson. In the Anderson structure, a register bar is provided above the paper supporting portion of the conveyor system, and the register bar is provided with a plurality of slots or races for the accommodation of a plurality of free-moving balls or spheres having peripheral portions projecting from the lower side of the register bar for rolling contact with sheets of paper carried on the conveyor. One or several of the register bars may be utilized, and are each slidably and adjustably positioned on an elongated support bar or rod for adjustment to selected positions along the path of travel of the paper sheets to be contacted by the balls. The number of the register bars used, and their positions along the supporting bar will be determined by the length of the paper stock being fed into the press or duplicator, and the points of pressure which are desired on the upper surface of each sheet of the paper as it moves on the conveyor. The register bars provided are mounted on their elongated supporting bars so that they may be adjusted axially therealong to desired positions in terms of their distance from the head stop. The register bars can also be adjusted vertically toward and away from their supporting bars so as to adjust the spacing between the periphery of the several balls, and the upper surface of the conveyor upon which the paper sheets are carried.
In the Anderson device, the balls or spheres are free-floating and thus can never impose any greater pressure or force upon the upper surface of the paper sheet than the weight of the balls. Further, the several balls carried in any one of the register bars act collectively and are evenly spaced with respect to the surface of the conveyor so that selective or independent adjustment of each ball's location cannot be attained. The Anderson structure further permits table whipping by the paper sheets in a way which is characteristic of all ball type guidance structures, since the balls are free to roll or turn in substantially any direction, and any spurious forces which tend to cause the paper sheets to cant or move sideways can do so without significant frictional resistance by the balls in contact therewith.